This invention relates to a controller for controlling the operation of a hydraulic motor.
In particular, the invention concerns a hydraulic motor controller comprising a directional valve for communicating pressure fluid from a pressure source to the motor, and including pilot pressure operated activating means, pilot valves connected to said activating means and to the pressure source, and a manually operable activating means mechanically connected to the directional valve via a coupling means.
A problem inherent in hydraulic motor controller of the above type, which comprises both pilot pressure operated activating means and a manually operable activating means, is the risk for unintentional or accidental activation of the directional valve by the pilot pressure activating means while controlling the motor operation by the manual activating means, or vice versa. In crane or excavator applications, which are the most common applications for this type of control system, accidental double activation of one or more directional valves would cause undesired and unexpected movements of crane or excavator arms which would be hazardous to personnel and equipment.
In previous control systems of this type several more or less successful attempts have been made to avoid undesirable activation by means of the control lever while the system is operated by remote control via the pilot valves and the pilot pressure activating means on the directional valve.
One such attempt comprises the application of a kind of hood which is intended to cover the activating lever or levers when the remote control is used, and which is coupled to a safety stop switch for inhibiting operation of the system via the remotely controlled pilot valves as the hood is removed from the lever or levers.
Another previously suggested way to avoid accidental activation of the directional valve by the control lever comprises a position detecting means coupled to the valve spindle of the directional valve and arranged to cause activation of a safety stop circuit if there is a discrepancy between the actual position of the valve spindle and a position the valve spindle should occupy at a certain pressure drop.
A third way previously suggested to solve the problem of how to prevent double activation of the directional valve was simply that the control lever or levers are arranged to be removed from the valve as remote control is performed.
The main object of the invention is to improve safety of hydraulic motor controller of the above described type by employing means by which double activation of the directional valve is safely avoided.
Another object of the invention is to provide a hydraulic motor controller which safely avoids hazardous double activation of the directional valve in a simple way and which is formed integrally with the control lever bearing.